1. Field of the Invention
This invention relates generally to the field of crank handles, and more specifically, to a retractable crank handle having a mechanism for aligning and locking the handle along the axis of rotation.
2. Description of the Prior Art
Crank handles are well known in the art. These handles may be employed to increased the torque applied to an axis of rotation and can be found on a variety of equipment. For example, such handles may be used to adjust the position of a work surface on fabricating equipment, to raise and lower retractable wheels on a trailer, or to rotate a take-up barrel on winching equipment. These handles generally are comprised of an arm, a handle attached to one end of the arm and a shaft attached to the other end of the arm. The shaft is aligned with the axis of rotation such that as a force is applied to the handle of the crank, a torque is applied about the rotational axis. The torque applied about the axis of rotation is, in part, a function of the length of the arm.
Various improvements have been made to the components of these crank handles. One such improvement is to place at least one hinged joint along the body of the crank handle so that at least a portion of the crank handle can be retracted. Specifically, this retractable portion rotates about the hinge such that the crank handle is less likely to protrude. This type of retractable crank handle is especially useful in instances where the protruding handle could be dangerous or interfere with the operation of the equipment to which the handle is attached. For example, after a crank handle has been used to adjust the height of a work surface on fabricating equipment, use of the equipment may be impeded by the protruding handle. By providing a hinged joint along the crank handle, at least a portion of the handle can be rotated to a position less likely to interfere with operation of the equipment. Those skilled in the art will understand that it is more desirable to locate the hinged joint along the shaft rather than the arm because this allows retraction of a greater portion of the handle.
Use of a hinge has presented various other difficulties and necessitated improvements to retractable crank handles. For example, retractable crank handles can be difficult to operate because alignment between the hinged portions may be difficult to maintain during rotation of the handle. Failure to keep hinged portions properly aligned renders the crank handle awkward to operate and may damage the handle by placing unintended forces on the hinge itself. Furthermore, when the handle is in its retracted position, there will be a tendency for the retracted portion of the handle to swing freely at the hinge, presenting difficulties such as those mentioned in the preceding paragraph. Thus the full benefit of the ability of the handle to be retracted is not realized. One solution to this problem has been to provide a pin or a ball and socket which are used to hold hinged portions in proper alignment. These solutions can also be employed to hold the retractable portion in its fully retracted position when the handle is not in use. However, one drawback to the solution utilizing a pin is that the pin must be inserted externally, thus complicating use of the crank handle. Additionally, the pin may not support the forces transferred through the handle. A drawback to the ball and socket is that the forces transferred at the joint between portions of the crank handle may be sufficient to urge the ball out of the socket causing the portions of the handle to become unaligned.
One solution to the problem with the ball and socket has been to provide a sleeve which is slidably mounted on the shaft or arm comprised of the hinged portions. The sleeve is designed so that it can be moved to a position along the shaft or arm so as not to interfere with the motion of the hinge when the shaft or arm is bent. However, when positioned adjacent the hinge, the sleeve prevents the hinge from pivoting and provides support between hinged portions, thus maintains alignment between the portions. Again, however, the sleeve is attached external to the handle and must be moved into position once the hinged portions of the crank handle are properly aligned.
Therefore, it would be desirable to provide a retractable crank handle that has an internal means for maintaining alignment. This means should allow a transfer of force between hinged portions without degradation of the force or damage to the crank handle. Additionally, it would also be desirable if the retractable crank handle can rotate or swing through approximately 180 to allow the retractable portion of the handle to be retracted in the least protrusive position. Lastly, such a handle should maintain a retracted position without the need for external fasteners to prevent the handle from swinging into an equilibrium position.